MMAjunkie.com (www.mmajunkie.com) today confirmed with Ultimate Fighting Championship officials that all 24 fighters who competed at this past month’s UFC 153 event in Brazil were tested, and Bonnar and Herman were the lone two competitors who failed the screen.

Bonnar tested positive for drostanolone, an anabolic steroid, while Herman’s screen was flagged for marijuana metabolites.

UFC 153 took place Oct. 13 at Rio de Janeiro’s HSBC Arena. Anderson Silva defeated Bonnar in the evening’s headliner while Herman was submitted by Antonio Rodrgio Nogueira in the co-main event.

With the lack of an athletic commission to govern the event, UFC officials took the role of overseeing the fight card. UFC exec Marc Ratner said the company has yet to issue a suspension to the fighters but is expected to do so sometime next week.

Bonnar earlier this week announced his retirement. His first positive test and subsequent suspension came after UFC 62, at which he dropped a unanimous decision loss to Forrest Griffin in their rematch. At that event, the Las Vegas-based Bonnar tested positive for a boldenone metabolite that resulted from anabolic-steroid use.

Following the suspension, Bonnar owned up to the infraction, saying he was trying to speed up the rehab of an injured elbow in time for the Griffin fight. The Nevada State Athletic Commissio suspended him nine months and fined him $5,000.

After a three-fight losing skid that included unanimous decision losses to eventual light heavyweight champion Jon Jones and UFC Hall of Famer Mark Coleman, Bonnar bounced back in 2010 with a second-round TKO win over Krzysztof Soszynski, then dominant unanimous decision wins over Igor Pokrajac and Kyle Kingsbury.

After a layoff of nearly a year, he got the chance of his career when he was asked to face Silva in Brazil in a light heavyweight bout on just a month’s notice. Bonnar came out swinging, but eventually succumbed to a Silva knee to the midsection and follow-up punches on the ground in the first round. It was the first time he had been stopped, not counting two stoppages from cuts.

“Huge thanks to every UFC fan out there!” the Carlson Gracie-trained Bonnar stated on Facebook, announcing his retirement. “All I ever wanted was to bring ya’ll some fun…hope u were entertained. Peace, love, & violence!”

Earlier this week, Bonnar’s wife gave birth to the couple’s first child.

Drostanolone is an anabolic steroid in the dihydrotestosterone family. Earlier this year, former Strikeforce light heavyweight champion Muhammed “King Mo” Lawal tested positive for the same substance.

For Herman, the failed test is also his second offense. The heavyweight was in 2011 scratched from a planned matchup with Mike Russow when he failed a pre-fight drug screen issued by the Texas Department of Licensing and Regulation. Herman later revealed marijuana was the offending substance, though he denied using the drug.

The remaining 22 fighters on the card all tested negative for drugs of abuse (such as marijuana and cocaine), as well as anabolic steroids and other performance-enhancers.

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